Epoxy resins have been widely used in the field of bonding, packaging, coating etc. Typically, epoxy resins are used in the type of "two-part", or called "A/B Part" type. Upon application, the main ingredient of the epoxy resin (Part A) and the curing agent (Part B) are admixed in a proper ratio in accordance with the epoxide equivalent weight (EEW) of the epoxy resin to the equivalent weight of the curing agent, and then cured. The application properties of the epoxy resins include curing rate which depends on the EEW thereof, the chemical structure and reactivity of the curing agents and the ratio between Parts A and B. Particularly, dosing the exact and accurate amounts of the epoxy resins and the curing agents is the most difficult step to control, especially, when the factors of equipment and manual-operation in the workplace are taken into account. These bothersome problems often arise when two-part type epoxy resins are used. Further, epoxy resins with high EEW (&gt;250) are in solid form at ambient temperature and accordingly, need to be formulated into liquid solution with solvents such that the cross-linking agent can be admixed homogeneously. Thus the use of solvent cannot be eliminated under this circumstance. In particular, the emission of the solvents from epoxy resin coating composition result in not only the economic loss but also the damages to the environment protection, safety and hygiene.
At present, the aqueous epoxy resin emulsions are prepared by adding emulsifiers to conventional solvent-type epoxy resins and adding water to emulsify the resulting mixture. However, emulsification exerted by the emulsifiers added is limited by the critical micelle concentration of the aqueous epoxy resin emulsions and therefore, aggregation will occur in the emulsions under the situation where the emulsions are arbitrarily diluted with water or are blended with other aqueous resins. As a result of the foregoing, such aqueous epoxy resin emulsions obtained thorough emulsification with emulsifiers are not widely accepted in this field.
It is therefore a worldwide trend to replace the conventional solvent type resins with aqueous resins.